 From 1967 to 1970 Wertheimer was Legislative Counsel to Representative Silvio Conte (R-MA) and Minority Counsel to the House Small Business Committee.In May 1971, he started working for Common Cause, a nonpartisan citizens' lobby where he was assigned to the issues of campaign finance reform and ending U.S. involvement in the Vietnam War.In 1976, Wertheimer was legal counsel for Common Cause during the "Buckley v. Valeo" case.